Many asked for recommendations how to hybrid and pair strings.
Most commonly:
- What tensions for mains and crosses? Any differentials?
- Which string for mains?
- Which for crosses?
- What gauge?
- Prestretch?
Personally, I do not enjoy hybrids. (I have even tried tri-brids and quad-brids!) No matter what I pair together - kevlar, syn gut, multifilament, natural gut, soft poly, stiff poly, fishing line, steel wire or grass trimmer line, it was extremely difficult to balance them well.
Inevitably, one string would dominate over the other. Usually, the feel and playing characteristics of the mains prevail. Once in a while, the crosses.
I am far from solving this puzzle, but I believe it has something to do with how the strings behave at different tensions.
When pulled to 55 lbs, the amount of total stretch observed in the following strings were:
- natural gut 6~7%
- synthetic gut 9~10%
- multifilament 10~12%
- poly 3~4%
- kevlar 1~2%
The numbers were in a range due to different batches and brands.
These same strings, when pulled an extra 10 lbs, bringing them to 65 lbs, yielded an incremental stretch of:
- natural gut 0.4~0.7%
- synthetic gut 0.8~1.1%
- multifilament 0.5~1.2%
- poly 0.1~0.3%
- kevlar 0%
The conventional wisdom is to string the softer string a couple pounds tighter. Using poly/syn gut at 53/55 lbs for example, would see them stretch about 3.5% and 9.5% respectively when strung.
However, during ball impact, the amount of additional poly stretch available is less than half that of the syn gut. Even though the strings are inter-weaved together, hard impacts bring the poly into deformation territories.
In other words, poly gets stretched beyond its elastic range and loses tension. Over time, the feel of the syn gut increases. (see "Impact Loss" in table below)
And that's only assuming one plays with the racket immediately off the stringing machine.
(from Tennis Warehouse University String Performance Database link)
When allowed to rest from being strung at 51 lbs each, the "Actual Pre-Impact Tension" has already dropped to 30/39 lbs! This differential would only get wider with every ball hit.
Having established this, then how about we string poly higher instead? Would that help to compensate for its larger pre-impact tension loss compared to syn gut?
Probably yes. But only for a while before impact tension loss brings down the tension again. How fast this happens depends on how tightly strung it initially was and how hard one hits the ball.
Another often overlooked factor is string gauge while pairing. Many choose the same gauge for hybrids, typically 17g or about 1.25mm.
Using the same example of poly/syn gut earlier, from my own measurements, the 1.25/1.25 mm combination would thin out to about 1.20/1.13 mm.
Below pic shows a 1.40mm syn gut became 1.25mm strung.
Below shows a 1.25mm syn gut thin to 1.10mm strung.
An easy way to calculate this diameter change would be to use the percentage stretch as a proxy. A 1.25mm string with 10% stretch, usually becomes 1.13mm (0.90 x 1.25) strung.
Simple engineering dictates, the thicker the material, the stronger the support. This could be another factor why the poly mains dominate when paired with syn gut in the same gauge. Well, but many people like it, so it's their choice.
Perhaps after reading this, one could start deducing why Federer is touted to be using 1.30mm gut mains and 1.25mm poly crosses:
0.93 x 1.30 = 1.209 mm
0.96 x 1.25 = 1.200 mm
The same gauge combination of 16G gut and 16L poly for Serena Williams as well? (link) And Sharapova? (link) And Nishikori? (link)
That said, my personal preference is still a full bed of the same string. Primarily for its ease of adjustment and consistency after play. If I were to cut strings out after every hour of play, then it might change.
After all, according to the Luxilon String Analysis at the 2013 US Open (link, refer pg 6-10), more than 70% of the competitors used the SAME STRING in both mains and crosses.
Special thanks to Irvin for highlighting that report. (link)
I could neither afford the time nor the money to keep restringing the fishing line after every 2-3 hours of play. Neither could I drop the idea after experiencing how well it played.
So a compromise need to be reached... I decided to convert two normal grommets to tie-off holes to faciliate greater ease of restring.
The pics below explain some of the what's and how's...
Note that each string's tie-off was anchored onto itself and not on another string.
Lest you are still wondering, this same string tie-off would allow me to restring ONLY whichever string that breaks...
Playtest:
- For this session of tennis, I pushed this stringbed very hard, trying to see if I could muscle it enough to snap it in an hour. Despite the four consecutive sets I played, the string prevailed.
- With proper pre-stretch, tension holding was very nice and string movement was very minimal. (Crosses 9 and 10 were pulled apart by me to check for notching)
- Notching was slight. About 1/4 of the diameter of the fishing line. If this lasts 6-8 hours, I would be more than satisfied!
- Comfort, spin and control remains excellent!
12May2014 update:
- A flat serve snapped the mains. Total play time was only about 5 hours.
- Despite the notching, the mains did not move much. All aspects like spin, control, power and comfort remained intact from first hit. I could not detect any deterioration in performance.
- Compared to the other fishing lines with syn gut (link), spin was still slightly better with this. Several serves and groundstrokes which my partner thought were long curled down in the last minute.
- Another prominent difference was that this premium Japanese line felt so much more softer and comfortable. Ball feel was better than the rest too.
Someone emailed me after reading my previous "Lendl Pattern" attempt (link).
He suggested I string the outside perimeter strings first, then the centre mains and crosses. Previously, I used a soft poly in the centre and syn gut around the perimeter.
The explanation was interesting and sounded convincing. Syn gut, being the softer string is almost always strung at a higher tension than poly. If the lower-tensioned poly was strung before the syn gut, he noticed that his racket frame would compress a little more during the syn gut stringing.
Since the frame was compressed, that led to some "tension loss" of the poly which made it play flat and dead from the first hit.
But how did he know the frame shortened since the racket was mounted?
Well... he claimed he dismounted the racket after completing the poly centre mains and crosses and measured hoop length and width. Complete with a starting clamp dangling at the side!
And he measured again after the softer perimeter strings were done. Shorter it was!
However, when the order was reversed, the dimensions remained constant, he claimed.
While I have several experimental frames to muck around with, I have no intention of finding out how my racket internals look like yet.
So for me, no dismounting halfway, but I'm game enough to give it a try. Nothing ventured, nothing gained.
Also, he added that soft poly strings play much better when strung with lock-out machines as compared to the constant tensioning of electronic and dropweight machines.
Below pic shows the higher-tensioned outer perimeter syn gut being completed first...
Could it be Lendl himself who sent the email? Or his stringer?
Playtest:
- I was pleasantly surprised how comfortable and yet controlled this stringbed played from the first hit!
- The sweetspot was right smack in the middle of the poly strings. It was very easy to find because it was so soft. I cannot recall when have I ever enjoyed this poly so much before.
- Spin seemed average to me, perhaps because I have been using so many extreme spin setups that this did not stand out. As usual, backhand slices were better than forehand topspins.
- Compared to the dead, stiff, boardy and powerless previous attempt (link), this felt like a totally different racket with different strings and different tension. Yet, everything was the same! Only the order of stringing was different!
- Pocketing was nice and harder flat hits were rewarded with accurate and powerful rebounds, with some unintended winners.
- Compared to syn gut, the poly pocketing was still "limited" in how much it gives before the feeling of hitting a wall took over.
- That was the only thing I disliked because the distinct stiff feel of poly was most clearly felt there, when the pocketing reached its limit.
Different strings are often used together to try to combine their strengths. Hybrids are very common.
But is there a need for, and can we use more than two different strings?
On the other hand, I find string properties very intriguing. For example, pull a syn gut too tight, and it can feel stiffer than a poly!
Too much power and hitting them long? Try swinging all out with the same syn gut at 25 lbs and you'll start hitting VERY short balls! Trampoline? Nah!
So string tension can also be used to alter a string's behaviour.
The variables in my mind are always how to:
- maximise spin
- improve comfort
- improve control
- increase sweetspot size
- move sweetspot higher
- reduce vibrations
- increase durability
Since each of the above variables demand a different string characteristic, I was wondering if "tri-briding" OR varying tension could better yield me the results I wanted.
Tri-briding
A soft multifilament was used as the mains, a smooth round poly for the crosses perimetered by a strong and fast fishing line.
In short, here's what I was trying to achieve:
- comfort + vibrations dampening + power --> multi
- spin + control + durability --> poly
- enlarge + move up sweetspot --> fishing line
Using three different strings require six knots. I had to modify the grommets to accomodate them.
Instead of a drill bit I used last time (link), I used a reversed thread "extractor" and it worked extremely well. It took only two minutes to change out those four grommets!
Here's some pics...
Varying Tension
With the same objective of optimizing the variables above, I used two-piece stringing of synthetic gut to see how it fares with the triple-strings option.
There was a lot of varying of tensions to soften or stiffen the syn gut at certain parts of the stringbed that I was trying to achieve.
Many previous attempts I've tried convinced me that grommet friction alone was enough to hold different tensions even with one-piece stringing. (link1)(link2)
You can see a lot of looping around of the string outside the frame. Very messy. Very unorthodox. To me, it's how it plays that counts!
Playtest:
Tri-brid
- Even with six tie-offs, tension holding was impressive. 24 hours after stringing, with no play, tension loss was only about 1.5lbs (15hz).
- After one hour of hard rallies and a game, the drop was only an additional 0.7lbs (7hz).
- From a "feel" perspective, I could not detect the usual tension drop after initial play. So I am very pleased with the tension stability.
- The distinctive feel of poly was dominant, even though it was strung as a cross. There was only a slight cushioning by the multi mains.
- The perimeter fishing line really stood out! It felt the best among the three types of string used. Soft, fast and powerful. So much so that I regret not using it in the mains instead.
- The sweetspot moved up significantly. I don't know how much but it felt higher, maybe by an inch or two, even without any weight changes!
- I was also a little shocked that the previous fishing line mains with poly cross (link) played SO MUCH better (spin, power & comfort) than this multi mains setup. So I guess it was worth paying the exorbitant price for that premium made in Japan fishing line.
- Not much string movement as shown in below pic but light notching can be seen on the multi mains.
Varied Tension
- Tension drop after 24 hours without play was 1.8lbs (18hz) and 0.7lbs (7hz) after one hour of play.
- From the first few hits, both my partner "D" and myself preferred this stringbed immediately.
- The largest difference came from the very huge sweetspot. This stringbed played immensely comfortable!
- What came to mind was how similar this felt compared to a full bed of natural gut!
- After less than 5 minutes of trying this, "D" wanted me to string this full syn gut setup for him.
- Spin, power, pocketing and serves were all much better than the other tri-brid. Just take a look at the amount of ball fur stuck on the strings!
- A slightly darker patch (from the 7th to 12th cross) can be observed on the strings from the ball contact.
29Jan2014 update:
I have always preferred the second session of tennis after a re-string.
Somehow, the stringbed just feels more responsive after that slight "breaking-in".
It's not tension loss as I had tried stringing a few pounds looser with the same string and racket, and it STILL played better on the second session.
So, to me, the second session would always be the acid test.
Tri-brid
- I did not measure the tension before, but after an hour of play, the frequency dropped another 2.3hz from the last reading in the last session of play. That's 0.2lbs. For six knots, I doubt it can get better than that.
- Compared to the perimeter fishing line, the multi mains felt dead! Yes, there was cushioning and dampening, but whenever I used this racket, I subconsciously adjusted my shots to contact much higher on the stringbed than I usually do. Simply because it felt much better there!
- Nothing fancy about spin nor control was observed today.
Varied Tension
- Tension drop was 5.6hz which was about 0.5lbs.
- Spin, control and comfort was impressive today.
- I know this sounds blasphemous, but the amount of spin I got from this string setup way surpassed whatever poly I've tried, even shaped poly. Just take a look at the amount of ball fur on the strings.
- The sweetspot is very sweet! There is a clear dark patch between the 5th to 12th cross. That's where the ball impact has been.
- Volleys were very easy to hit and place compared to the tri-brid.
- With the varied tension, pocketing felt much more controlled without the high rebound angle.
- To test myself, I lowered my net clearance during game play. I was able to aim deep while keeping the clearance below 24 inches with about 90+% success rate. So stringbed predictability was more than acceptable.
- Both flat and heavy spin shots performed accurately without any problems in aiming nor directional control.
- Flat serves, which usually demanded "stiff as a board" stringbeds, performed well enough. Strangely, I actually enjoyed the pocketing during serves!?!? I got the feeling that the pocketing added some pace. It was a single bounce in the service box then straight to the wall with a thud. I have no idea at what speed that was going but I liked it.
12Feb2014 update:
- Another several hours of play has both been added to the tri-brid and varied tension.
- With use, comfort, spin, dampening and sweetspot size are clearly diverging between the two rackets.
- The tri-brid played alright in the first session but every aspect dropped steadily after that. The varied tension fared much better and felt so much more consistent throughout.
- This could be due to the different wear and tear patterns of the three different strings acting up on me.
- Somehow, the multi mains in the tri-brid felt the worst to me. It felt dry, crispy, was deeply notched and offered not much vibration dampening. (See pic below for mains notching)
- The varied tension maintained its natural gut-like feel. Only difference is the speed of resilience is slightly slower. I like this enough to make this my regular setup but will continue to tweak the varied tensions on the stringbed.
